The present invention relates to an industrial robot with a device for guiding a cable set and to a method for and a use of the robot.
With industrial robots, it is usual to arrange the cable set within the robot. With welding robots, it is just as usual that the cable set is run on the outside of the robot. During welding work within the car industry, the robot must be able to reach inside confined spaces to weld. If the cable set then runs freely outside the robot, there is a risk that it will get caught in other items found in the assembly of cars, especially when the cable set is unprotected around the wrist and tool of the robot. Getting caught in this way leads in turn to damage to the robot and involuntary interruption of operations that has a detrimental effect on the production.
The term cable set here refers to process cable sets for, for example, welding electrodes, power supply for the actual tool and power supply for the robot. In addition, the term can include extra lines for, for example, different needs of the customer.
Document WO 85/01686 shows an industrial robot equipped with welding equipment. The cable set is run along the outside of the robot to a welding tool. Here the tool has the possibility to both rotate and pivot/bend more than 90xc2x0 without this causing any greater stress in the cable set.
Document EP 0 873 826 shows a wrist for an industrial robot. The wrist is constructed from three parts (16,17,20) that are joined with one another to rotate and designed so that they form an open through channel. Cables and lines for the power supply are led through the wrist and out to a tool. The objective of the wrist is to fully enclose the cable set. The advantages that are specified are that the dimensions of the arm are reduced, that there is less risk that the cable gets caught and that there is less of a problem with deformation and torsion of the cables and lines. Inside the wrist, cable set 49 is firmly attached with two clamping means 50 and 51 that are arranged within the hollow elements 40 and 47 respectively. The design allows a maximum bending of the wrist of 90xc2x0 through rotation of the parts 16 and 17 and simultaneous rotation of the cable set. The different cables, lines and tubing of the cable set lie spread out radially and are kept apart from one another over the whole cross-sectional area of the clamp.
Problems arise when the work that the robot is to perform requires that the robot can bend its wrist more than 90xc2x0 and that it at the same time must protect the cable set. Cables for electrical power for welding electrodes, power supplies for tools and the robot, electrical signal cables for transferring information from sensors at the welding head, lines for pressurised air and coolants, etc., must be able to accommodate the required bending during simultaneous rotation despite them offering a large resistance to simultaneous bending and rotation. The supply lines in the European patent document are arranged spread out radially in clamps 50 and 51 and the design does not allow bending of the cable set by more than 90xc2x0.
When manufacturing industrial robots with a large freedom of movement of the tool, the need thus arises to arrange the cable set so that it is protected within the robot in a way that allows bending of the cable set by at least 90xc2x0 during simultaneous rotation.
This need cannot be fulfilled by any of the industrial robots shown in the cited patent documents.
When designing robots, the object according to the invention is to design the robot so that its cable set runs protected the whole way through a central cavity through/in the robot. When the robot is used as, for example, a welding robot, it is required that the robot is equipped with a special cable set at the same time as good manoeuvrability of the welding tool is also needed. Within the. car industry in particular, a lot of welding work is done with robots. The welding tool must be able to rotate and turn for the robot to reach inside confined spaces in a manner suitable for welding techniques. The requirement for good manoeuvrability of the welding tool in turn requires that the cable set must be able to accommodate bending by 90xc2x0 and more and rotate at the same time.
During simultaneous bending and rotation of a cable set, the individual lines are subjected to elastic strain and torsion. Since the robot moves in repeating cycles, this occurs all the time at the same places in the cable set, which over time leads to wear. The individual lines and cables are made of different materials dependent on their function. Their working life thus depends partly on the properties of the materials. The individual lines and cables behave differently due to their geometric location in the cable set. In locations where the deformation and torsion of the cable set is large, unwanted wear of the individual lines occurs. The working life of the lines thus also depends on their physical location in the cable set.
It is therefore necessary to replace a worn or alternatively damaged cable set after a certain period of operation to eliminate the risk of unwanted production stoppage.
The development of cable sets for robots is moving towards a more flexible system where the robot is equipped according to a standard concept. The customer then decides how the robot is to be equipped prior to delivery. In a flexible system, it is also possible for the customer to change the field of use for the robot.
In the light of the needs named above, a robot ought to be designed so that it is easy to replace or alternatively add to the cable set.
The object of the present invention is thus to achieve a robot in which a cable set is arranged in a compact/space-saving and protected manner. A further object of the invention is to arrange the supply lines so that they allow their bending by more than 90xc2x0 and rotate a sufficient number of times without problem.
The solution according to the invention is to let a part of the cable set accommodate the rotational movement and another part of the cable set accommodate the bending movement and to arrange a guiding supporting means to allow a transition between rotational and bending movements.